JP2006022681A - Turbo type fluid machine and stepped sealing device used thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a stepped sealing device capable of fully reducing a leakage from the mouth ring part of a turbo type fluid machinery, such as a pump, treating incompressible fluid. <P>SOLUTION: The turbo type fluid machinery is provided with the mouse ring part, having a seal function, between the side plate of an impeller 3 and a pump casing 1. The mouse ring part consists of the mouse ring 4 on the side plate of the impeller; and a mouse ring 5 situated on the unrotary wall surface side of the casing, and the mouse ring 4 is constituted that the impeller suction side is formed in a small diameter and the outlet side in a large diameter, and it has a step-wise difference part in a level of at least two or more steps. The mouse ring 5 is formed in a labyrinth-shape having a convex part 5a and a concave part 5b, a fine gap part E being a narrow radial gap is formed between the convex part 5 and the mouse ring 4, and a flow passage space part formed into an enlarged part of a radial gap is formed of the concave part 5 and the difference part in a level of the mouse ring 4. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a turbo fluid machine having a mouth ring that seals a rotating slit portion between a non-rotating body such as a pump casing and an impeller side plate, and a stage used for the mouth ring portion in the turbo fluid machine. The present invention relates to an attached sealing device.

  The turbo fluid machine includes a rotating shaft and an impeller attached to the rotating shaft, and performs work by a difference in angular momentum at the impeller entrance and exit that is generated when the impeller is rotated by the rotating shaft. For this reason, except for the case of full open blades, one or two rotating slits are formed between the non-rotating body and the impeller. The leakage flow that flows out from the high pressure side of the impeller to the low pressure side through this slit portion is a loss. This leakage loss may be as large as 20% of the total loss when a high-efficiency fluid machine has a low specific speed.

  As represented by the following equation, the leakage flow q is proportional to the square root of the sectional area A of the slit portion and the differential pressure ΔP before and after the slit portion, and is inversely proportional to the square root of the flow resistance ζ of the slit portion. For this reason, various ideas have been made to increase the flow resistance of the slit portion.

ここでαは定数である。

Here, α is a constant.

  The flow resistance ζ of the slit portion is classified into two types: a friction loss when flowing through the slit portion, and a sudden expansion loss and a sudden reduction loss due to changes in the shape and cross-sectional area of the slit portion. The friction loss is determined by the gap size of the gap, the flow velocity of the working fluid, and the coefficient of kinematic viscosity. Therefore, it is necessary to avoid contact between the impeller and the non-rotating body. There is a limit to increasing the resistance by lengthening. For this reason, in most cases, the structure of the sealing device that reduces the leakage loss of the mouth ring portion is a structure that effectively incorporates changes in shape and cross-sectional area. For example, a staircase-shaped labyrinth seal structure described in Patent Document 1 or the like Is used.

JP-A-11-343996

  However, the conventional labyrinth seal structure in the mouth ring part uses the adiabatic compression effect by rapidly expanding the area from the convex part of the labyrinth seal to the concave part for the flow resistance, so the turbo type that handles incompressible fluid such as a pump When used in a fluid machine as it is, a sufficient leakage flow reduction effect cannot be obtained.

  An object of the present invention is to provide a turbo fluid machine that can sufficiently reduce leakage flow from a mouth ring portion in a turbo fluid machine that handles incompressible fluid such as a pump, and that is easy to manufacture and highly reliable. The object is to obtain a stepped seal device.

  In order to achieve the above-mentioned object, the present invention is provided between a rotating shaft provided in a casing of a pump, an impeller attached to the rotating shaft, a side plate of the impeller, and the pump casing. In the turbo type fluid machine including a mouth ring portion having a sealing function, the mouth ring portion includes a mouth ring on the impeller side plate side and a mouth ring provided on the non-rotating body wall side of the casing, and the blade The car side plate side mouth ring has a configuration in which the impeller suction side has a small diameter and the exit side has a large diameter and has at least two stepped step portions, and the mouth ring provided on the non-rotating body wall side has a convex portion. A labyrinth shape having a concave portion, and forming a narrow radial gap between the convex portion and the impeller side plate side mouth ring, and the concave portion and the impeller side plate side mouth ring. It is obtained by forming the flow path space which is a enlarged portion of the radial clearance between the stepped portion.

  Here, it is preferable that the axial positions of the radial wall portion of the impeller side plate side stepped portion and the radial wall portion of the non-rotating body side labyrinth-shaped concave portion coincide with each other or substantially coincide with each other.

  Further, the flow path space portion formed by the stepped portion of the impeller side plate mouth ring and the non-rotating body side labyrinth-shaped concave portion has a substantially rectangular shape, and the radial position of the narrow gap portion of the narrow radial gap is When the flow path space portion is configured by a step portion and the labyrinth-shaped concave portion, and is configured to be positioned on the outer diameter side from the radial center position of the flow path space portion provided on the downstream side of the slit portion. good. In particular, the radial position of the slit portion has a height in the range of ½ to 3/4 from the bottom surface of the flow path space portion formed by the step portion and the labyrinth-shaped concave portion in the outer diameter direction. It is preferable to provide it at a position.

  Another feature of the present invention is that a rotating shaft provided in the casing, an impeller attached to the rotating shaft, a mouth ring portion provided between the side plate of the impeller and the casing and having a sealing function. In the turbo type fluid machine, the mouth ring part is configured by an impeller side plate side mouth ring and a non-rotating body wall side mouth ring of the casing, and the impeller side plate side mouth ring is configured by the impeller suction side. The non-rotating body wall surface side mouth ring has a labyrinth-like convex portion and a labyrinth-like concave portion, and the labyrinth-like convex portion and the blades. A flow path space portion that forms a narrow gap portion between the car side plate side mouth ring and an enlarged portion of the radial gap between the labyrinth-shaped concave portion and the step portion of the impeller side plate side mouth ring Formed in the flow channel space, from the inner diameter side of the slit portion, in that a structure to generate a secondary flow (D) toward the outer diameter side than the slit portion.

  According to still another aspect of the present invention, there is provided a stepped seal device that forms a narrow step-like gap between a rotating body and a stationary body of a turbo fluid machine, wherein the sealing surface structure on the rotating body side has a low pressure. It has at least three steps with a small diameter on the side (suction side) and a large diameter on the high pressure side (discharge side), and the sealing surface structure of the stationary body has a labyrinth-shaped convex portion and a labyrinth-shaped concave portion. A flow path space portion that forms a narrow gap portion between the labyrinth-shaped convex portion and the rotating body-side seal surface, and is an enlarged portion of a radial clearance between the labyrinth-shaped concave portion and the step portion of the rotating-body-side seal surface. And a secondary flow (D) directed from the inner diameter side to the slit section toward the outer diameter side from the slit section is generated in the flow path space.

  In the above, it is particularly preferable that the material of the member constituting the sealing surface on the stationary body side is a thermoplastic resin. Further, if a plurality of labyrinth grooves shallower than the depth of the labyrinth-like concave portion are formed on the inner wall surface of the convex portion of the non-rotating body side mouth ring constituting the slit portion, the leakage flow can be further reduced.

  According to the present invention, even in a turbo fluid machine that handles an incompressible working fluid, the flow resistance of the fluid flowing in the stepped portion provided in the stepped seal device can be increased. Leakage flow can be reduced.

  Further, since the axial dimension of the labyrinth-shaped convex portion can be increased with respect to the labyrinth-shaped concave portion, high-precision machining is facilitated, and an easily manufactured turbo fluid machine and a stepped seal device used therefor can be obtained. .

  Furthermore, since significant swirling flow can be prevented from occurring in the flow path space formed in the step portion of the stepped seal device, leakage loss can be achieved without impairing reliability even when used in a pump handling liquid containing slurry. Can be reduced.

  If the non-rotating body side sealing member is made of a thermoplastic resin, the thermoplastic resin has low friction and excellent wear resistance, and has self-lubricating properties, thereby preventing seizure. As a result, the gap between the seal portions can be further reduced and the amount of leakage can be further reduced, so that the effects of the present invention can be maximized.

  In a turbo type fluid machine that handles incompressible fluid such as a pump, as shown in FIG. 6, a labyrinth structure including a concave portion and a convex portion is provided on the impeller side plate portion side, and incompressibility due to centrifugal force generated in the labyrinth It is conceivable to increase the flow resistance by utilizing the secondary flow effect of the fluid. However, with this structure, there is a problem that the amount of leakage significantly increases when the relative axial position of the rotating body and the stationary body changes. Further, in the configuration as shown in FIG. 6, the axial dimension of the convex portion 4 b is small with respect to the concave portion 4 a of the mouth ring 4 constituting the labyrinth portion, and machining is difficult, and high-precision machining is required.

  For this reason, in a turbo fluid machine such as a pump that handles an incompressible fluid, as shown in FIG. 7, a multi-stage structure in which the axial length of the slit portion is longer than the axial length of the gap portion. It is also conceivable to use an attached sealing device. However, when this multi-stage stepped seal device is used, the leakage loss at the stepped seal portion is not negligible as a percentage of the total loss as described above, and the efficiency of the 1% level in the market today It becomes a serious problem in competition.

  Hereinafter, specific embodiments of the present invention that can sufficiently reduce the leakage flow from the mouth ring portion in a turbo fluid machine that handles incompressible fluid and that are easy to manufacture will be described with reference to the drawings.

  An embodiment of the present invention will be described with reference to FIGS. 1 is a longitudinal sectional view of a main part showing a turbo fluid machine (centrifugal pump) of this embodiment, FIG. 2 is a sectional view for explaining the detailed structure of a mouth ring part in the centrifugal pump shown in FIG. 1, and FIG. FIG. 4 is a detailed cross-sectional view showing the structure of the main part of the stepped seal device part in the mouth ring part.

  As shown in FIG. 1, the turbo fluid machine (centrifugal pump) in the present embodiment has a rotating shaft 2 driven by a driving machine (not shown) disposed in a casing 1. A plurality of impellers 3 are arranged in multiple stages. Since a rotating slit is formed between the casing 1 and the impeller 3 that is a rotating body, the purpose is to suppress the leakage flow of the working fluid from the impeller outlet side to the suction side through the rotating slit. Thus, a mouth ring 4 (see FIG. 2) is provided on the impeller side plate 3a side, and a mouth ring 5 (see FIG. 2) is also provided on the non-rotating body wall surface 1a of the casing 1 facing this.

  As shown in FIG. 2, in this embodiment, a stepped sealing device is formed on the mouth ring 4 and 5 part. The mouth ring 4 provided on the impeller side plate 3a has a small diameter on the impeller suction side and a large diameter on the outlet side, and is configured in a stepped shape of two or more steps (three steps in this embodiment). In addition, the mouth ring 5 on the non-rotating body wall surface 1a side has a labyrinth shape, and a step portion (radial wall portion) 4c (see FIG. 4) of the impeller side mouth ring 4 and a mouth ring 5 are provided for each step. An axial position (a leak flow downstream end position of the radial slit portion) A of the labyrinth concave portion 5b and the radial wall portion 5c (see FIG. 4) are configured to coincide with each other.

  Since the centrifugal pump of the present embodiment has the above-described configuration, the double cylindrical portion in which a narrow radial gap E is formed between the labyrinth-like convex portion 5a and the mouth ring 4 portion of the impeller side plate, and the labyrinth-like concave portion 5b and the mouse. By the enlarged portion of the radial gap formed by the stepped portion of the ring 4 portion, it is possible to combine the portion where the area of the radial gap serving as a leakage flow passage rapidly expands and the portion where it suddenly decreases. Moreover, the double cylindrical part radial position in each step (step part) of the stepped seal device part can be shifted. As a result, as in the case where the conventional labyrinth seal is applied to an incompressible fluid, the fluid flows out from the labyrinth convex portion (tooth portion) 5a to the flow path space portion (concave portion) 5b as a jet without being compressed. Since the flow passage space portion 5b is not short-circuited, the flow resistance of the rotating slit portion can be effectively increased and the leakage flow can be reduced.

  Further, the step portion (recessed portion) 5b of the mouth ring 5 on the stationary side is configured as a labyrinth that is enlarged from the radial position of the narrow gap portion (radial gap E) to the outer diameter side. For this reason, as shown in FIG. 4, the centrifugal force effect acts on the fluid in the vicinity of the vertical wall surface 4c on the impeller side plate 3a side to generate a secondary flow D that is radially outward, and this secondary flow D is effective. As a result, the resistance of the rapidly expanding portion is increased, and the sealing effect can be remarkably improved as compared with the stepped sealing device as shown in FIGS.

  Furthermore, compared to the stepped seal device as shown in FIG. 6 or FIG. 7, the volume of the flow path space in the labyrinth-shaped recess 5b can be increased and the interference action by the secondary flow D is increased. The swirl flow C (see FIG. 3) in the space (recessed portion 5b) can also be reduced, and it becomes a resistance when the swirl flow is formed again in the next-stage narrow gap portion (radial clearance E on the downstream side of the leak flow), As a result, the outflow / inflow resistance in the stepped seal device can be increased, and the effect of greatly reducing the amount of leakage can be obtained.

  FIG. 5 is a detailed cross-sectional view of a stepped seal device portion showing another embodiment of the present invention, and shows another example of the stepped seal device provided in the mouth ring portion. In this embodiment, the flow path space portion constituted by the step portion of the mouth ring 4 portion on the impeller side and the labyrinth-shaped concave portion 5b on the non-rotating body side is formed into a substantially rectangular shape, and the stationary side mouse in this flow path space portion The labyrinth-like concave portion 5b side of the ring 5 is configured to expand to the outer diameter side from the radial position of the narrow gap portion (radial gap) E, and in these respects, the configuration is the same as that of the above-described one embodiment. In this embodiment, the labyrinth groove 5d shallower than the recess 5b is provided on the inner wall surface of the mouth ring 5 on the non-rotating body side in the slit portion E.

  Since the present embodiment is configured as described above, the leakage flow B from the upstream labyrinth-shaped recess 5b can be prevented from short-circuiting to the next-stage labyrinth-shaped recess 5b ′, and the flow resistance of the slit E can be effectively reduced. And leakage flow can be reduced. In particular, the radial position of the slit E is set to 1/2 to 3/4 of the height of the flow path space formed by the impeller step portion and the non-rotating body side labyrinth-shaped concave portions 5b, 5b ′ (of the flow path space If it is provided in the range of 1/2 to 3/4 height position from the bottom surface toward the outer diameter direction, the secondary flow works effectively, and a remarkably swirling flow C in the circumferential direction is also formed in the labyrinth-shaped recess. Not. As a result, when handling slurry water containing silt, it is possible to prevent wear of the slit portion due to rotation of the silt, and even in the case of a high-pressure pump, at the step portion outlet side wall surface due to high flow rate leakage flow B The risk of erosion can be reduced. Furthermore, since the labyrinth groove 5d is formed on the casing side wall surface of the slit portion E, the amount of leakage flow, sliding torque, and swirl flow can be further reduced.

  The material of the mouth ring 5 on the non-rotating body side constituting the stepped seal device is desirably a thermoplastic resin. Thermoplastic resin has good heat transfer characteristics, can form a rotating slit with a narrow gap size, and it is easy to remove sliding heat even if the mouth ring contacts or bites foreign matter. is there. Therefore, the sealing performance can be improved, a multi-stage configuration is possible without changing the length in the impeller axial direction, and the performance of the stepped sealing device can be maximized.

As described above in detail, according to the present embodiment, even when the working fluid is incompressible, the flow resistance in the sealing device of the mouth ring portion can be increased, and the circumferential swirl in the labyrinth-shaped recess is significantly increased. Since no flow occurs, even in the case of a liquid containing slurry, an effect of reducing leakage loss without impairing reliability can be obtained.

The longitudinal section of the important section of the turbo type fluid machine (centrifugal pump) which shows one example of the present invention. Sectional drawing explaining the detailed structure of the mouth ring part in the centrifugal pump shown in FIG. The cross-sectional view which shows the shape of the labyrinth-like recessed part 5b vicinity shown in FIG. FIG. 3 is a detailed cross-sectional view showing a structure of a main part of a stepped seal device portion in the mouth ring portion shown in FIG. 2. The detailed sectional view of the stepped seal device part which shows other examples of the present invention. Sectional drawing explaining an example of a general stepped sealing apparatus. Sectional drawing explaining the other example of a general stepped sealing apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Casing, 1a ... Non-rotating body wall surface, 2 ... Rotating shaft, 3 ... Impeller, 3a ... Impeller side plate, 4, 5 ... Mouth ring, 5a ... Labyrinth-like convex part, 5b, 5b '... Labyrinth-like concave part, 4c, 5c ... radial wall portion, 5d ... labyrinth groove, A ... radial slit portion axial position, B ... leakage flow, C ... swirling flow, D ... secondary flow, E ... slit portion (radial gap) ).

Claims (9)

A turbo type comprising a rotating shaft provided in a casing of a pump, an impeller attached to the rotating shaft, and a mouth ring portion provided between a side plate of the impeller and the pump casing and having a sealing function. In fluid machinery,
The mouth ring part is composed of a mouth ring on the impeller side plate side and a mouth ring provided on the non-rotating body wall side of the casing,
The impeller side plate side mouth ring is configured to have a stepped step portion of at least two steps with a small diameter on the impeller suction side and a large diameter on the outlet side,
The mouth ring provided on the non-rotating body wall surface has a labyrinth shape having a convex portion and a concave portion, and forms a narrow gap portion with a narrow radial gap between the convex portion and the impeller side plate side mouth ring, A turbo-type fluid machine, wherein a flow path space portion that becomes an enlarged portion of a radial clearance is formed by the step portion of the recess and the impeller side plate side mouth ring.   2. The turbo according to claim 1, wherein axial positions of a radial wall portion of the impeller side plate side stepped portion and a radial wall portion of the non-rotating body side labyrinth-shaped concave portion are matched or substantially matched. Type fluid machine.   The radius of the slit portion of the narrow radial gap according to claim 1 or 2, wherein the flow path space portion formed by the step portion of the impeller side plate mouth ring and the non-rotating body side labyrinth-like concave portion has a substantially rectangular shape. The directional position is a channel space portion constituted by the stepped portion and the labyrinth-shaped recess, and is positioned on the outer diameter side from the radial center position of the channel space portion provided on the downstream side of the slit portion. A turbo fluid machine, characterized in that it is configured to do so.   In Claim 3, The radial direction position of the said slit part is the range of 1 / 2-3 / 4 toward the outer-diameter direction from the bottom face of the flow-path space part comprised by the said level | step-difference part and the said labyrinth-shaped recessed part. A turbo fluid machine provided at a height position of In a turbo fluid machine, comprising: a rotating shaft provided in a casing; an impeller attached to the rotating shaft; and a mouth ring portion provided between a side plate of the impeller and the casing and having a sealing function. ,
The mouth ring part is composed of an impeller side plate side mouth ring and a casing non-rotating body wall side mouth ring,
The impeller side plate side mouth ring has a structure having at least three steps with a small diameter on the impeller suction side and a large diameter on the outlet side,
The non-rotating body wall side mouth ring has a labyrinth-like convex portion and a labyrinth-like concave portion, and forms a slit portion between the labyrinth-like convex portion and the impeller side plate side mouth ring, and the labyrinth-like concave portion And a step portion of the impeller side plate side mouth ring form a flow passage space portion that becomes an enlarged portion of a radial clearance, and the flow passage space portion is formed from the inner diameter side with respect to the slit portion. A turbo fluid machine, characterized in that a secondary flow (D) directed toward the outer diameter side is generated.   6. The turbo fluid machine according to claim 1, wherein the non-rotating body side mouth ring is made of a thermoplastic resin.   The turbo according to any one of claims 1 to 6, wherein a plurality of labyrinth grooves shallower than the depth of the concave portion are formed on an inner wall surface of the convex portion of the non-rotating body side mouth ring constituting the slit portion. Type fluid machine. In a stepped sealing device that forms a narrow step-like gap between a rotating body and a stationary body of a turbo fluid machine,
The seal surface structure on the rotating body side has at least three step portions with a small diameter on the low pressure side (suction side) and a large diameter on the high pressure side (discharge side),
The seal surface structure of the stationary body has a labyrinth-shaped convex portion and a labyrinth-shaped concave portion, and forms a slit portion between the labyrinth-shaped convex portion and the rotating body-side seal surface, and the labyrinth-shaped concave portion and the rotation A flow passage space portion that becomes an enlarged portion of the radial gap is formed with the step portion of the body-side sealing surface, and the flow passage space portion is formed on the outer diameter side from the slit portion from the inner diameter side than the slit portion. A stepped seal device for use in a turbo fluid machine, characterized in that a secondary flow (D) directed toward the bottom is generated. 9. The flow path space portion according to claim 8, wherein a material of a member constituting the sealing surface on the stationary body side is a thermoplastic resin, and a radial position of the slit portion is formed by the step portion and the labyrinth-shaped recess. A stepped seal device for use in a turbo fluid machine, characterized in that it is provided at a height position in the range of 1/2 to 3/4 from the bottom surface to the outer diameter direction.

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